The present invention relates to a headlamp for an automobile in which a light source unit with a light source mounted therein is tiltably supported by an aiming mechanism with respect to a housing which is mounted and fixed to a vehicle body, and more particularly to a headlamp for an automobile having a structure in which a light source unit is cantilevered by an aiming mechanism.
To describe a headlamp for an automobile by citing as an example a reflector-movable type headlamp in which a reflector is tiltably supported in a lamp body, as shown in FIGS. 8 and 9, the rear surface side of a reflector 202 on which a light source 206 is fitted is cantilevered with respect to a lamp body 201, i.e., a housing which is mounted and fixed to a vehicle body, by means of an aiming mechanism comprising two aiming screws 203 and 204 extending through the lamp body 201 in the depthwise direction as well as one tilting fulcrum 205.
A pair of brackets 202a and 202b are projectingly formed on upper left and right portions of the rear surface of the reflector 202, and a ball bearing nut 205a constituting the tilting fulcrum 205 is fitted in one bracket 202a, while a screw supporting nut 207, to which the aiming screw 204 is threadedly engaged, is fitted in the other bracket 202b. In addition, a boss 202c is projectingly provided at a position below the bracket 202a, a bracket 202d is threadedly fastened to this boss 202c, and a screw supporting nut 208, to which the aiming screw 203 is threadedly engaged, is fitted in the bracket 202d.
FIG. 8 is a front elevational view of the reflector, and the aiming screws 203 and 204 respectively extend perpendicular to the plane of the drawing. The aiming screws 203 and 204 are respectively supported rotatably on the rear surface wall of the lamp body 201, and supporting points (nuts 207 and 208) for supporting the reflector 202 by means of the aiming screws 203 and 204 are arranged, for example, perpendicular to the tilting fulcrum 205 as viewed from the front side of the lamp. Through the rotating operation of the aiming screws 203 and 204, the reflector 202 is tilted about a horizontal axis Lx (a straight line connecting the tilting fulcrum 205 and the nut 207) and a vertical axis Ly (a straight line connecting the tilting fulcrum 205 an the nut 208), respectively, so as to adjust an illuminating angle of the lamp.
Also in a unit-movable type headlamp in which a lamp body/reflector unit (hereafter simply referred to as the unit), whose reflector is integrally formed on an inner peripheral surface of a lamp body, is tiltably supported with respect to the lamp housing, the structure is also adopted in which the unit is cantilevered with respect to the lamp housing by means of an aiming mechanism having one tilting fulcrum and two aiming screws. The unit is tilted by the rotating operation of the two aiming screws so as to adjust the illuminating angle of the lamp.
Thus, with the headlamp for an automobile, by rotatingly operating the two aiming screws, the light source unit for setting the illuminating direction of the lamp is tilted vertically and horizontally with respect to the housing (the lamp body in the case of the reflector-movable type headlamp, and the lamp housing in the case of the lamp body/unit movable type headlamp), so as to adjust the illuminating angle of the lamp.
As described above, the brackets for connecting the aiming mechanism (203, 204, and 205) are provided on the rear side of the reflector, and are generally formed integrally on the reflector 202 formed of a synthetic resin, as shown at reference numerals 202a and 202b. However, there are cases where it is difficult to form the brackets integrally with the lamp body, depending on the shapes of the reflector and the brackets to be formed or due to the relationship with the position for mounting the aiming mechanism. In such a case, as shown in FIG. 9, the plate-shaped bracket 202d, which is formed separately from the reflector 202, is provided by being fixed by a screw.
However, since the reflector 202 is cantilevered by the aiming mechanism as described above, a pressing force Q1, which is attributable to the moment about the horizontal axis Lx (tilting fulcrum 205) due to the self-weight W of the light source unit (the reflector 202 with the light source 206 fitted thereon), acts particularly on the lower position among the three connecting portions between the reflector 202 and the aiming mechanism, i.e., on the bracket 202d connected to the aiming screw 203. Por this reason and partly due to the fact that the position in the bracket 202c for being fixed to the reflector 202 and the position therein for connection to the aiming screw 203 are verticall offset, the aforementioned pressing force Q1 and a reaction force Q2 (=Q1) acting via the aiming screw 203 are applied to the bracket 202d. Hence, there are possibilities that the bracket 202d becomes deformed as shown by the imaginary line in FIG. 9, thereby making the smooth rotation of the aiming screw 203 difficult and making it impossible to effect aiming adjustment with high accuracy.